The amino acid sequence of the spinach basic cupredoxin plantacyanin.

We describe the amino acid sequence of plantacyanin isolated from spinach leaves. This small basic copper-binding plant cupredoxin contains 91 amino acids (accession no. S70746) and its theoretical average mass of 9788.2 Da was confirmed by electrospray ionization mass spectrometry. When compared to the sequences of other plant cupredoxins, the most similar homologs were cucumber basic blue protein and stellacyanin from Laquer tree with 44-58% identical residues. Other known plant cupredoxins were significantly less similar which may allow to divide the plant cupredoxins into two subgroups, the single-domain cupredoxins (plantacyanin, cucumber basic blue protein and stellacyanin) and the two-domain, hydroxyproline-containing cupredoxins (cucumber peeling cupredoxin, basic blue protein from Arabidopsis thaliana and horseradish umecyanin).